Add ability to override nginx ssl engine as not defined

If by default engine set to 'salt' and there is no way to unset it.

Change-Id: Iaac14c2afc9a8604642145ddbc0e0aacb8ca6b46
Related-Prod: PROD-27578
(cherry picked from commit b8cb543c4803c18db2c723a9b7fc454d4f86c46b)
4 files changed